Self-controlled aircraft landing gear



i April 4, 1950 05s. HOOBLER I 2,502,522

' SELF-CONTROLLED AIRCRAFT LANDING GEAR Filed Aug. 14, 1945 4 Sheets-Sheet 1 Bmuentor Q Mammy S? u v a Omcug I I April4, 1956 f Filed Aug. 14, 1945 ,E. s HOOBLER 2,502,522

SELF-CONTROLLED AIRCRAFT LANDING GEAR 4 Sheets-Sheet 2 3nventor B g 7 A i A Etta-N035 I April 4, 1950 E. .s. HOOB'LER 2,502,522

' SELF-CONTROLLED AIRCRAFT LANDING GEAR F i1ed- Aug. 14; 1945 I 7 '4 Sheets-Sheet 5 Enventor April 4, 1950 I E. s. HOOBLER 2,502,522

. SELF-CONTROLLED AIRCRAFT LANDING GEAR Filed Aug. 14, 1945 4 Sheets-Sheet 4 III v 3Iwentor mwmbwbz Patented Apr. 4, 1950 UNITED STATES PATENT OFFICE SELF-CONTROLLED AIRCRAFT LANDING GEAR Claims.

The invention relates generally to aircraft undercarriage construction or landin gear, and more particularly to aircraft landing gear which is self-controlled for landing or taking off cross wind.

It is well known that in landing or taking off an aircraft, the best practice is to direct the aircraft against the direction of the Wind, but there are many cases where it is desirable or necessary due to restricted landing field or runway areas, to land or take off cross wind, that is, at an angle to the direction of the wind. Moreover, in cases where it is necessary to make a forced landing because of motor trouble or for some other reason, it is oftenimpossible to land safely in an available field or clearing in a direction other than cross wind.

In order to make a cross wind landing with a conventional three control aircraft, it is necessary for the pilot to practice many hours before he becomes skillful enough to execute the performance withoutdamage, shock or stress on the aircraft. In making a cross wind landing, the pilot must hold his ship on a crabbed or angular approach, that is, headed into the wind at an angle tothe direction of drift, until he is within a few inches of the ground. Then in a split second, he must put up the inner wing by manipulating its aileron and simultaneously reverse the rudder so as to line up his Wheels with the direction of force in which the plane is moving.

Obviously, such landing operation requires great skill and is seldom executed perfectly, so that shock and strain are imparted to the aircraft, and in severe'cases the plane'is wrecked and the occupants injured or killed.

Taking off cross wind also requires much skill because the pilot must judge the angle of drift and manipulate his controls to. head the :plane into the wind at the proper angle just as it leaves the ground.

Recently, the trend in construction of modern aircraft for civilian use has been toward simplicity in operation and control, so that the average person can learn to fly easily and with substantial safety. Thus, if the smaller aircraft for civilian use is provided with a two-control mechanism, the pilot has only his control stick or wheel to think of in making his landing or take off,

because the usual separate rudder pedals or controls are incorporated in the wheel or stick as well as the aileron controls. Accordingly, when the pilot turns his steering wheel to make a turn, he turns his rudder and simultaneously operates his ailerons.

While this type of control simplifies greatly the operation of the aircraft, it prevents making a cross wind landing safely because the ailerons and rudder cannot be operated independently as is necessary during thelast few seconds just before contacting the ground in a cross wind landing. Accordingly, a forced landing cross Wind may result in a crash landing with fatal or severe injuries to thepilot and passengers, together with damage to the aircraft itself.

Prior cross wind landing controls have been proposed which require the pilot to observe drift indicator instruments and to set his landing wheels accordingly in preparation for a cross wind landing. Such constructions require two or three additional operations and involve accurate judgment on the part of the pilot, and frequently the angle of drift changes materially as the ship nears the ground, so that the pilot does not have time to reset his wheels, and severe shock and damage to the aircraft and possible injuries may result.

In taking off cross wind with such prior constructions, the pilot is required to first set his landing wheels according to his estimate of the angle of drift, and if his estimate is inaccurate the plane will not be crabbed or headed into the wind at the proper angle.

Moreover, such prior constructions complicate the pilots duties and are contrary to the present trend toward simplifying the flying operation.

It is therefore an object of the present invention to provide a novel and improved aircraft landing gear which will overcome all of the foregoing disadvantages.

Another object is to provide a novel aircraft landing control which is adapted to make a twocontrol aircraft suitable for landing and taking off cross wind.

Another object is to provide a self-controlled aircraft landing gear which can be applied to a two-control aircraft without requiring additional controls or complicating the pilots operation.

A further object is to provide a novel self-controlled aircraft landing gear which is adapted for landing cross wind without any shock or strain to the aircraft.

Another object is to provide a novel landing gear which enables an aircraft to move down a runway in a crabbed position for taking off cross wind, so that the aircraft leaves the ground headed into the wind at the proper angle, Without requiring the pilot to make any corrections for drift.

A still further object is to provide a novel land- A further object is to provide a novel cross wind landing gear which is so constructed as to prevent vibration or shimmy. of the wheels during landing or take off.

Finally, it is an object of the present invention to provide a simple and self-aligning landing gear for aircraft, which is adapted to align the wheels with the directionof force when the plane first lands, and then to gradually bring the main landing wheels into alignment with the fuselage as the plane slows to a stop. I

These and other objects apparent from the following description, are accomplished by the parts, elements, constructions, arrangements, combinations and sub-combinations, comprising the present invention, the nature of which is set forth in the following general statement, and preferredembodiments of which are set forth in the following description and illustrated in the accompanying drawings, in which is particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

In general terms, the nature of the invention may be stated as including an aircraft having acaster mounting for each of the main landing wheels with a linkage or connecting rod arrangement for tying said wheels together to cause them to turn together about vertical pivots, said linkage embodying vibration or shimmy dampener and being operatively connected to a third landing wheel for turning it in the same direction as the main wheels, and a control wheel or steering device connected to the said operative connection means for steering said third landing wheel.

Inthe accompanying drawings, preferred embodiments of the invention are shown by wayof example.

Figure l is a diagrammatic plan view of an aircraft embodying the presentinvention, about to land cross wind on a runway, and having its landing wheels aligned or parallel with its fuselage;

Fig. 2 is a similar view of the aircraft immediately after contacting the runway, showing the landing wheels aligned with the runway;

Fig. 3 is a diagrammatic plan View of the landing gear or undercarriage of an aircraft embodying the present invention, with the wheels in the position of being aligned with the fuselage as in Fig. 1;

Fig. 4. is a similar diagrammatic plan view on a reduced scale, with the wheels turned to a position such as shown in Fig. 2;

Fig. 5 is a similar diagrammatic plan view showing the front steering wheel turned and the main landing wheels parallel with the fuselage;

Fig. 6 is a longitudinal cross sectional View of the novel vibration or shimmydampener embodied in the linkage connecting the main land ing wheels;

Fig. 7 is a cross sectional view thereof as on line 5-1, Fig. 6;

Fig. 8 is a cross sectional view thereof as on line 8-4;, Fig. 6;

Fig. 9 is an enlarged fragmentary vertical sectional view, partly in elevation of one of the main landing wheel caster mountings;

Fig. 10 is a fragmentary plan sectional view thereof as on line lol0, Fig. 9;

Fig. 11 is a'detached perspective view of the cam surface bearing washer embodied in the wheel mounting of Fig. 9.

Similar numerals refer to throughout the drawings.

While the present invention is shown by way 'of example as embodied in the landing gear or undercarriage of a tricycle type landing gear, it is to be understood that the invention may be applied to aircraft having a tail steering wheel, and to aircraft having separate rudder controls without a steerable tail wheel, without departing from the'scope of the appended claims forming part hereof.

Referring first to Figs. 1 and 3, the novel unsimilar parts dercarriage or landing gear is shown embodied in a tricycle landing gear of an aircraft P having two main landing wheels l2 located on opposite sides of the fuselage F, and a front steerablenose wheel 13 located under the front end of the fuselage F and in a vertical plane passing through its axis w--a:. I 1

In conventional planes having the tricycle type landing gear, the main landing-wheels 12 cannot be turned about a vertical axis, but are always I aligned longitudinally withithepl'ane, that is,

are parallel with the axis :c-zr, in the position shown in Figs. 1 and 3. Thus a two-control plane of this type cannot he landed cross wind as in Fig. 1 because the'wheels it would skid on contacting the runway and damage or crack up the plane.

The present invention provides an off center pivotal mounting or caster mounting for each of the wheels 52 so that they can rotate or caster to a limited extent about the vertical pivots indicated .at the points it. Thus, the plane can approach a runway R in a crabbed position or at an angle headed into the wind, the direction of'which is represented by the arrows A in Figs. 1 and 2,-and as'the plane settles onto the ground, the main wheels l2 will, upon contacting the runway, turn in .the direction of force indicated by the. arrow B, which is the resultant of the force of the cross wind and the force of the forward motion of the plane along the axis ."cw. The wheels l2 are operatively connected to'the front wheel l3 so that as they turnthey immediat'elyturn the wheel 53 in the same direction, and as wheel it settles upon the runway, it is already parallel with the same.

Thus, no skidding of any of the wheels results from contact with'the runway, and the plane can roll forwardly parallel to the runway" without any danger of shock or damage or cracking up the plane, and without requiring any preliminary operations by the pilot.

The linkage or connecting rod arrangement which ties the wheels 52 together so that they turn in unison preferably includes lever plates l5 which turn with the wheels l2 about the pivots M in a manner to be described later herein. The rear ends it of the levers 15 are preferably pivotally connected at IT'to the ends of a cross rod [8, and the front ends l9 of'the levers I5 are pivotally connected at 20 to the ends of across rod 2|. Accordingly, as one of the wheels turns on its vertical pivot and turns the lever with it, such motion is transmitted by the rods 18 and 2| to the opposite lever l5 and wheel l2 so that the wheels l2 turn in unison.

A vibration or shimmy dampener indicated generally at 22 is preferably mounted by means of suitable brackets 23 upon the frame of the airplane and the rod I 8 is arranged to reciprocate within the dampener 22 for cushioning the lateral shock on the wheels l2 as they hit the ground and turn in the direction of the resultant force. The construction of the dampener 22 will be described more fully later herein.

The means operatively connecting the wheels l2 with the steering wheel l3, which is shown in this case as a nose wheel, to turn wheel l3 in unison with wheels l2, preferably includes cables 24a and 24b connected at their rear ends by means of suitable clamps 25 to the rod 2| on opposite sides of the axis :c-r, and being trained intermediate their ends around pulleys 26 which are suitably journalled at fixed locations On the frame of the aircraft. The forward portions of the cables 24a and 24h extend from the pulleys 26 forwardly parallel to the axis .r-a: and are attached to the yokes 21 of pulleys 28a and 28b. The shafts 29 of pulleys 28a and 28b are movably journalled in a well-known manner upon the frame of the aircraft, so that the pulleys 28a and 2% move longitudinally of the aircraft and.

connected at 3| to theouter ends of a-lever 32v which rotates with the nose wheel I3 about its vertical pivot 33. The inner strands of the cables a and 30b are shown at 340. and 34b and extend from the pulleys 28 diagonally forward to cross each other with their forward ends being piv.

otally connected to opposite ends of the elevator control shaft 35 on which the steering post 36 of a control wheel 31 is mounted in a usual manner. The elevator control shaft 35 is oper-,

atively connected by suitable means (not shown) to the elevators of the aircraft, so that as the shaft 35 is axially rotated by oscillating the wheel 31 back and forth, elevators are controlled in a.

conventional manner.

The connection between the post 36 and the control shaft 35 may include suitable mechanism which transmits the axial rotating motion of the steering wheel 31 and post 36 to-the shaft 35.

in such manner that it swings horizontally about its center pivot 38, in the manner shown in Fig. 5. The elevator control shaft 35 is also pivotally connected to the ends of cables 39 which are operatively connected in a usual manner to the aileron and rudder controls, so that axial rotation of the control wheel 3'! turns the elevator control shaft 35 about its vertical axis 38 and controls both the ailerons and rudders and steers the wheel I3 independently of the main landing, wheels 12; while at the same time the control,

aircraft is adaptedfor steering the auxiliary wheel J3 wi ho t e i ethe m w ls. l

The connection of the elevator controls to the control wheel 31 together with the aileron and rudder controls represents an embodiment of the so-called two-control aircraft, and follows broadly the principles of conventional aircraft of that type. The present invention provides a means for adapting said principle to an undercarriage in which the main wheels caster on vertical pivots and their turning motion is transmitted to. the front wheel, which is steerable independently of the main wheels.

As shown in Figs. 1 to 5 inclusive, as an aircraft such as shown in Fig. 1 embodying the present invention approaches a runway R at an angle headed into a cross wind, the'wheels l2 and 13 are aligned longitudinally with the plane, and the pilot does not need to read any instruments or 'make I any preparations for landing.

As the plane settles onto the runway R, according to usual practice the main wheels [2 strike first, and because of their caster mountings are immediately turned in the'direction of the resultant force indicated by the arrow B which is the direction of the runway. As the wheels turn in this direction, as indicated in Figs. 2 and 4, the dampener 22 cushions the lateral shock and the transverse motion of tie rod 2| pulls the left cable 24a and its pulley 28a rearwardly and allows right cable 241) and its pulley 28b to move forwardly, as indicated in Fig. 4, with the result that the left cable 30a pulls rearwardly on lever 32 and the right cable 30b moves forwardly. Thus, the front wheel. [3 of the undercarriage is turned immediately in a direction'parallel with the main landing wheels [2, without any rotation of the control wheel 31, and as the front wheel [3 settles on the runway all three landing wheels l2 and 13 are in a position to roll forwardly down the runway R, as best indicated in Fig. 2.

If it is desired to steer the aircraft while the plane is taxiing upon a landing field, the same is accomplished by steering the front wheel [3 with the control wheel 31 in the same manner as the conventional tricycle landing gear. In this case, as shown in Fig. 5, the main landing wheels l2 remain aligned longitudinally with the aircraft, or parallel to the axis :zz-x, so that the pulleys 28a and 28bremain fixed with respect to the airplane, and as the wheel 31 is turned to steer the front landing wheel l3, the control shaft 35 turns on its center pivot 38 and causes a pull on left cable 36a to turn the front wheel as shown without disturbing the aligmnent of the main wheels l2.

Referring to the shimmy dampener indicated generally at 22, as shown in Figs. 6, '7 and 8, the cross rod 18 passes axially through the cylindric housing 46 of the dampener, and the ends of the housing preferably have suitable packing glands 4| providing seals around the rod I8. As shown, one end of the housing may be a removable plate 42 which is screwed in the housing for assembly purposes. Thus, the housing 46 provides a sealed cylinder for containing suitable fluid such as oil.

The rod l8 has a piston box indicated generally at 43 secured thereon as by bolts 44, and adapted for reciprocating within the cylinder 46,

; which is secured to the frame of the aircraft by the brackets 23. The piston 43 includes a cylindric outer wall 43' slidable in cylinder 46, and end walls 45 and 46, the end Wall 46 being preferably screwed on the vcylindric wall 43 for assembly purposes. The end walls 45 and 46 are asoagtee its: end walls; whichis. radially spaced from the outer'periphery'fisl ofathediaphsagm; The clear= ance between 5! and 5'2 is such as to provide a. flow of oil through the? piston s'ufiicient to permit relatively gradual movement-f the rod! and piston: longitudinally oi the cylinder; but a: movenrenti's yieldingly resisted.

Accordingly. as thewheels I! turn. suddenly',. as by striking the ground. at an angle to the direction of motion? of the" plane, the shock of the turninamotion: imparted thereto is trans mittenv to the rod It: to move itthrough the cylinder id, and such motion is yiel'dingly re sistecl by" the resistance to the flow of fluid through the pistonbox 43; caused by the floating diaphragm 48. The pressure: of the fluid on; the diaphragm causes it to move longitudinally on the rod t8 against the action of spring 4-9. or 58;. which gradually increases the clearance between: the outer rim? 54 of the diaphragm and the boss' 51?; and allows passage of a greater amount of fluid throughout the piston. box. Thus, the

shock of. the turning motion. of wheels I2 is cushioned, preventing oscillation or shimmy of the wheels as the plane lands, or taxis.

Referring to' the novelv mounting construction" for the main landing wheels Hi. the mountings for both wheels. t2 are-identical-,.and one is showrr in Figs; 9; I0 and 11. The lever plate" it has a depending splined post 55 which is coaxial with. and slidable vertically within the splineelbore 56' of. the vertical pivot shatt on. which the landing wheel: 2 2' is carried; The pivot shaft 5 is siidably and rotatably mounted? ina tubular housing 58-, and a absorbing helical spring. 59 cn'girdles the shaft 51 Within the housing 58'; The upper: end of the spring as abuts arr. annular shoulder. N1 in the housing 58 and the lower endor the spring abuts a washer 6! which is tortieally sl idable on the shaft 5%, and normally abuts bushing 6'2. at the bottom endof the housing.-

As shown in Fig. 11, the Washer 8 is provided with diametrically opposite ribs 63, and these ribs are slidable in slots '34 Within the housing: 5-8, so that the shaft 5? earl slidevertically within the washer iii, but the washer. 52 is held against rotation within the housing. The bottom washer 6i provided with cam surfaces as shown, which may be diametrically opposite grooves or curved recesses t5, and these grooves are normally positioned directly over mating. curved ribs 65 formed on a collar El which is secured to the bottom end of the shaft 5T. Such normal position is occupied when the main wheels ii are parallel with the fuselage.

A bracket car 58 depends axially from the bottom of shaft 5'? and is provided with bear-- ing 59 in which a horizontal pivot pin it? is journalled, and lever means comprising the yoke or clcvis H which mounts the Wheel 2' at its rear end and is carried intermediate its endson" said horizontal pivot pin Ill; The rear end of the yoke I la mounts'ani axle its on. which the wheel 12E may be journalled usual: fashion. and. asuitable brake may be incorporated in; the wheel? in. accordance with well known. practice; but the same forms no. part of: the present invention.

The wheel. l-2'. isa'ccordingly mounted" oil-center on the: shaft El to provide a caster mounting which causes the: wheel to follow in the direction of. resultant force or motion or the airplane whenv the wheel contactsthe ground. The: front end or theyoke 7! has a ball and socket counection indicated. at it with the lower end. or. a: link 14, and the upper'end of link M has a. similarbail and socket connection. indicated at "5-5 with the side of the housing. 58 in which the pivot shaft 511 is journall'edi The function of this connection between the" front ends of the yoke H and thehousing 58: i's'to' limit swingingv movement. ofiwheel i2 about? pivot shaft 5:1 and: to' provide aime'an's urging the wheels Hi to return to their aligned position: of Fig, 3 when: they have been turned by contact with the ground as in a crosswindlandin'g; and the function of the cooperating! cam surfaces 55* and $6 is to aid. in returning wheels i2 totheir aligned positions.

In the operation". of the: novel. mounting construction, as the wheel i2 strikes the ground on a. cross wind landing: and is immediately turned towardthe direction of force; the: lateral. shock throws the": front end of. the yoke ll' atthe joint laterally to oscillate about the joint '15 as a pivot; and at the same time the impact on the wheel i2 throws the horizontal pivot pin iii upweirdly tngfether. with the pivot shaft 57 and compresses the springsttfl As the spring 53* absorbs" the impact, the curved ribs 66' ride rotatabiy' on the camsurfaces or recesses of the Washer 51 which-is held against rotation.

The weight or? the plane exertedon pivot pin Til has the effect of a downward: pull on the joint 18' tending: toreturn it to center or normal position with respect to joint 7'5, and at the same time, the pressure between the cam surfaces; 55' and it tends/to rotate the shaft Ell to-norrn-al axial position of Fig. 9. Consequently, after the plane has landed. and begins to slow downv on the; runway. the: combined efiect of these two forces willtend. to gradually bring the wheels :2 back into alignment para'liel with the fuselage as the plane slows to: a stop, and the pilot can easily straighten out the plane.- by steering the front wheel N to alignit with'the runway.

In order: to hold the rear wheels in alignment with. the plane for taxiing purposes, a locking devicemaybe' provided on one ofthe main wheel mouz itings,v and as shown. Fig. 9: may include a locking pin i i which is adaptedto enter a hole T8 in" the lever plate It when the wheels are aligned. the plane as in theiposition ofFig. 3. Preierabl'y, the pin Tl has a collar Tl attached: thereto intermediate its ends, and is slidably' mounted at its endsin fianges l9 and pro je'cting from the housing 58'. Compression springs SI and- El are interposed between the collar i1 and the flanges 19 and 80, and a bell crank 82 is pivoted on the flange 80 and has one arm 83" engirdling' the pin ll and adapted for compressing spring 8| to urge the pin upweirdly.

The other arm of bell crank 82 is operatively connected by means of a cable 84 to a suitable han-d'l'ever 85 located" near the control 31. Thus, when the pilot desires to-lock the wheels I2 for 75 taxiing, he pulls the handl'ever 83 to actuate the lever arm 83 and urge the pin 11 upwardly I against the lever plate 15, and when the wheels [2 are brought into alignment, the pin 11 will snap into the hole 78 and lock the wheels in that position. When the hand lever 85 is released. the pressure of spring 8| will snap the pin Tl out of the hole 18 and release the wheels l2.

The present invention provides a self-controlled landing gear which is adapted to be applied both to aircraft of the two-control type and three-control, for landing cross wind, and enables a pilot to make such landing without preparatory manipulations of the controls and without estimating the angle of drift or reading instruments to determine the same. With the present invention, the pilot makes a landing cross wind by merely holding his plane in a crabbed position such as to keep the plane moving in the direction of the runway as it approaches the ground, and as the landing wheels strike the ground, they align themselves with the resultant direction of force so that the plane can roll freely and safely in that direction.

With an aircraft embodying the present invention, the pilot merely steers the nose or tail wheel as he moves down the runway, depending on whether the landing gear is tricycle or the conventional type having a steerable tail wheel. If the invention is applied to the type of aircraft having rudder pedals and no steerable wheel, the steering can be done by manipulating the brakes in a usual manner. a

If a plane embodying the present invention makes a landing cross wind, as previously described, the novel caster mounting tends to return the wheels in alignment with the plane as the plane slows down. This straightening up of the plane can be accelerated to some extent by manipulating the brakes in a usual fashion as in the ordinary airplane.

In taking ofi cross wind with an aircraft embodying the present invention, as the plane moves down the runway, the effect of the cross wind is to swing the plane into a crabbed position at an angle to the Wind, so that as the lane leaves the ground, it is in proper position for the take off, that is, it is nosed into the wind while moving in the direction of the resultant force. With prior constructions, in which the main landing wheels cannot pivot on vertical axes, the pilot is required to use utmost skill in swinging the plane into a crabbed position at the instant it leaves the ground; otherwise, damage or crackup to the plane may occur due to sudden drift of the plane.

In prior constructions requiring preparing for taking oif by setting the Wheels at a particular angle depending upon the direction of .the cross wind with respect to the runway, the pilots estimate of the angle of drift may be inaccurate, and in any event, additional operations and skill on the part of a pilot are involved.

Thus, the present invention provides a simple and. inexpensive landing gear construction which overcomes the disadvantages of prior constructions with respect to landing or taking off cross wind, and which is easily applied to all conventional types of aircraft.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior are, because such words are used for descriptive purposes and are intended to be broadly construed.

Moreoven'the embodiments of the improved construction illustrated and described are by way of example, and the scope of the present invention is not limited to the exact details of the various parts.

Having now described the features of the invention, the new and useful devices, constructions, arrangements, combinations, sub-combinations, parts and elements, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.-

I claim:

1. Aircraft landing gear construction including laterally spaced main landing wheels and an auxiliary landin wheel spaced longitudinally thereof, means providing a free turning caster mounting for each of the main landing wheels to permit them to caster freely when engaging the ground, means operatively connecting said main landing wheels for causing them to turn in unison on their mountings, a vibration dampener embodied in said main wheel connecting means for preventing shimmy of the main wheels on landing, control means op'eratively connecting said main landing wheel connecting means to said auxiliary wheel for turning it in unison with said main landing wheels, and means attached to said control means for steering said auxiliary wheel independently of said main landing wheels.

2. In an aircraft having laterallyspaced main landing wheels and an auxiliary landing wheel spaced longitudinally thereof, a pilot-operated control device for steering the aircraft in flight, free turning caster mountin means for the main landing wheels to permit them to caster freely when engaging the ground, means operatively connecting said main landing wheels, single vibration dampener means for cushioning lateral shock imparted to said main landing wheels on striking the ground when landing, control means operatively connecting said main landing wheels with said auxiliary landing wheel for turning said auxiliary wheel with said main landing wheels as they'turn on their castermounting means, and means connecting said control means to said pilot-operated control device for steering said auxiliary wheel independently of said main landing wheels.

3. In an aircraft having laterally spaced main landingwheels, a caster mounting for each of said wheels including a housing, a vertical shaft pivoted in said housing, means in said housing yieldingly resisting upward movement of said shaft in the housing, a washer slidably engirdling said shaft and slidably and non-rotatably mounted in said housing, cooperatin cam means onsaid washer and shaft tending to rotatively return said shaft to its normal axial position, a lever having a horizontal pivotal connection intermediate its ends with the bottom end of said pivot shaft, means journalling a main landing wheel on one end of said lever, and a link having a universal connection at one end with the other end of said lever and a universal connection at the other end of said link with said housing.

4. Aircraft landing gear construction including laterally spaced main landing wheels and an auxiliary landin wheel spaced longitudinally thereof, a free turnin caster mounting for each main wheel including a housing, a vertical shaft slidable and rotatable in said housing and meansmounting a main landing wheel elf-center on said shaft; tie means operatively and rigidly connecting said shafts ,for turning said main landing wheels in unison, single vibration damp- .ener means connected to said shafts for preventing shimmy of said main landing wheels on landing, and control means operatively connecting said tie means to said auxiliary wheel for turnin the same in unison withsaid landing wheels.

5.. Aircraft landing :gear construction including laterally spaced main landing Wheels :and an auxiliary landing wheel spaced longitudinally thereof, a free turning caster mounting having a vertical pivot for each main wheel, means operatively and rigidly connecting said main wheels for turning onsaid pivots in unison, means operatively connecting said main wheels to said auxiliary wheel for causing it to turn with the free castering movement of said main landing wheels, and releasable means for locking the main'wheels in normal position in alignment with said aircraft.

ERNEST S. HOOBLER.

REFERENCES CITED The following references are of record in the file of this patent: 5

UNITED "STATES PATENTS Number Name Date 1;844 ,1-86 Short l Feb. 19., 1932 2,211,484 Warner Aug. 3, 1940 2,222,350 Maclaren Nov. 26, 1940 2,291,571 Cleveland July 28, 1942 2,393,110 Kops et a1. Jan. 15, 1946 FOREIGN PATENTS Number Country Date 9 413 Great Britain 1907 

